vp_dev->msix_vectors should be initialized before allocating
msix_affinity_masks, otherwise vp_free_vectors will not free these
objects.

unreferenced object 0xffff88010f969d88 (size 512):
  comm "systemd-udevd", pid 158, jiffies 4294673645 (age 80.545s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff816e455e>] kmemleak_alloc+0x5e/0xc0
    [<ffffffff811aa7f1>] kmem_cache_alloc_node_trace+0x141/0x2c0
    [<ffffffff8133ba23>] alloc_cpumask_var_node+0x23/0x80
    [<ffffffff8133ba8e>] alloc_cpumask_var+0xe/0x10
    [<ffffffff813fdb3d>] vp_try_to_find_vqs+0x25d/0x810
    [<ffffffff813fe171>] vp_find_vqs+0x81/0xb0
    [<ffffffffa00d2a05>] init_vqs+0x85/0x120 [virtio_balloon]
    [<ffffffffa00d2c29>] virtballoon_probe+0xf9/0x1a0 [virtio_balloon]
    [<ffffffff813fb61e>] virtio_dev_probe+0xde/0x140
    [<ffffffff814452b8>] driver_probe_device+0x98/0x3a0
    [<ffffffff8144566b>] __driver_attach+0xab/0xb0
    [<ffffffff814432f4>] bus_for_each_dev+0x94/0xb0
    [<ffffffff81444f4e>] driver_attach+0x1e/0x20
    [<ffffffff81444910>] bus_add_driver+0x200/0x280
    [<ffffffff81445c14>] driver_register+0x74/0x160
    [<ffffffff813fb7d0>] register_virtio_driver+0x20/0x40

v2: change msix_vectors uncoditionaly in vp_free_vectors

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>